| Maxim Tobacco Company Limited | Professional & scientific | 1989 |
| Maxted Limited | Administrative & support | 2003 |
| MAY Events Ltd | Arts & recreation | 2025 |
| Maya Catering Ltd | Hospitality | 2022 |
| Maya Cuisine Ltd | Hospitality | 2023 |
| Mayfield Distilling Company Ltd | Manufacturing | 2017 |
| Mayflower Meadow (Angmering) Management Company Limited | Households | 2022 |
| Mayi Staffing Solutions Ltd | Administrative & support | 2024 |
| Maynard Performance Consulting Ltd | Professional & scientific | 2025 |
| Mayne Roofing and Build Ltd | Construction | 2025 |
| Maypole Management Company Limited | Households | 2020 |
| MB Ventures Ltd | Professional & scientific | 2021 |
| Mb&H Limited | Administrative & support | 2022 |
| MC Precision Landscapes Limited | Professional & scientific | 2025 |
| MC2 Therapeutics Limited | Manufacturing | 2005 |
| Mcalear Management Consultants Limited | Professional & scientific | 2013 |
| Mcbride&Co. Limited | Construction | 2024 |
| Mcdonaldspharm Limited | Professional & scientific | 2009 |
| Mcewen Software Limited | Information & communication | 2017 |
| Mcfb Limited | Administrative & support | 2026 |
| Mcgavigan Consulting Limited | Professional & scientific | 2025 |
| Mcivor&Team Limited | Professional & scientific | 2012 |
| Mclaren Whitson Ltd. | Professional & scientific | 2017 |
| Mcompany Ltd | Real estate | 2017 |
| Mcpe LLP | | 2013 |
| Mcshane Construction Limited | Construction | 1983 |
| ME Goodeve & SON Limited | Real estate | 2024 |
| Meaco (U.K.) Limited | Wholesale & retail | 2003 |
| Meaco Holdings Limited | Financial services | 2020 |
| Meaco Property Limited | Real estate | 2024 |
| Mead Insurance Services Limited | Administrative & support | 1997 |
| Meadow Health Limited | Health & social care | 2023 |
| Meadow School Limited | Education | 2024 |
| Meadowbank (Guildford) Management Limited | Households | 2002 |
| Meadowbank Garden Services Ltd | Other services | 2014 |
| Meadowlark Productions LLP | | 2023 |
| Meadows in the Mountains Limited | Administrative & support | 2012 |
| Meadway Design and Construction Limited | Construction | 2011 |
| Mebo Bridal Ltd | Manufacturing | 2019 |
| Mechanic VAL Ltd | Wholesale & retail | 2025 |
| MED Cleaning Services Ltd | Administrative & support | 2024 |
| Mede Limited | Wholesale & retail | 1999 |
| Medevolve Limited | Professional & scientific | 2012 |
| Media Insurance Services Limited | Other services | 1999 |
| Media on Demand Streaming Limited | Information & communication | 2011 |
| MEDIA12 Group Ltd | Professional & scientific | 2024 |
| MEDIA4SHARE Limited | Administrative & support | 2023 |
| Medialabs Network UK Ltd | Information & communication | 2012 |
| Medianett Publishing Limited | Administrative & support | 2021 |
| Medicalspace Ltd | Information & communication | 2022 |
| Medication Management Ltd | Health & social care | 2014 |
| Mediheal Ltd | Information & communication | 2023 |
| Medithera Consulting Limited | Health & social care | 2011 |
| Medpharm Holdco Limited | Financial services | 2018 |
| Medpharm Limited | Professional & scientific | 1999 |
| Medusatech Ltd | Information & communication | 2009 |
| Meenu Transports Ltd | Transport & logistics | 2021 |
| Megan Clement Limited | Professional & scientific | 2023 |
| Megatraders Limited | Professional & scientific | 2004 |
| Meley Consulting Ltd | Professional & scientific | 2021 |
| Melissa Manners Publishing Limited | Information & communication | 2025 |
| Melita Fitness Limited | Arts & recreation | 2014 |
| Melliss LLP | | 2002 |
| Melrose Education Holdings Limited | Education | 2021 |
| Melrose Education Investments Limited | Education | 2021 |
| Melrose Education Limited | Education | 2021 |
| Melsimpex Ltd | Wholesale & retail | 2019 |
| Melt and Co. Desserts Ltd | Manufacturing | 2015 |
| Melville Court Management Limited | Households | 1971 |
| Meme's 94 Construction Ltd | Construction | 2024 |
| Memories Maker Limited | Construction | 2013 |
| Memz Turkish Barbers Ltd | Other services | 2019 |
| Men's Sheds Limited | Extraterritorial | 2019 |
| Menage Recruitment Limited | Administrative & support | 2024 |
| Mentoring 4 Success (UK) Limited | Other services | 2021 |
| Mentow Enterprises Limited | Real estate | 1996 |
| Meoglow Limited | Real estate | 1976 |
| Mera Management Limited | Construction | 1997 |
| Meraki Fit Ltd | Arts & recreation | 2017 |
| Mercury Strategic Advisors Ltd | Professional & scientific | 2022 |
| Meridian Biogas Ltd | Energy | 2024 |
| Meridian Defence Ltd. | Manufacturing | 2026 |
| Meridian Swimming Pools Limited | Professional & scientific | 2001 |
| Merino Capital LLP | | 2010 |
| Merino Industries Ltd | Professional & scientific | 2015 |
| Merino Management Ltd | Professional & scientific | 2010 |
| Merino Properties Limited | Professional & scientific | 2010 |
| Merino Property Holdings Limited | Professional & scientific | 2012 |
| Merivale CS Ltd | Professional & scientific | 2013 |
| Merlin Cars Ltd | Wholesale & retail | 2018 |
| Merlin House Properties Limited | Construction | 2007 |
| Merlin Renewables Limited | Energy | 2012 |
| Merrow Business Park Management Ltd | Households | 1994 |
| Merrow Capital Ltd | Financial services | 2024 |
| Merrow Cyprien Ltd | Professional & scientific | 2015 |
| Merrow Downs Residents Group Ltd | Other services | 2023 |
| Merrow Interiors Limited | Wholesale & retail | 1987 |
| Merrow Park Dental Practice Ltd | Health & social care | 2021 |
| Merrow Technical Services Limited | Professional & scientific | 1978 |
| Merrywood (Thames Ditton) Management Company Ltd | Households | 2023 |